1. Field of the Invention
The present invention is generally related to eye examining instrumentation and, more particularly, to a hand held instrument used for inspecting the optic nerve of a patient's eye.
2. Description of the Prior Art
Glaucoma is a disease of the eye which causes partial or complete loss of sight. Glaucoma is characteristically accompanied by hardening of the eyeball, increased intraocular pressure, and damage to the optic nerve. Proper diagnosis of glaucoma should include measurement of the intraocular pressure, study of visual field tests, and an examination of the optic nerve. The treatment of glaucoma requires relieving pressure in the eye; this is typically done by the use of drugs, lasers or surgery, all of which entail risks to the patient. It would therefore not be sound practice to prescribe such treatment for glaucoma if the optic nerve was undamaged. Patients may, for example, have a high pressure condition in the eye with no damage to the optic nerve. This condition is called ocular hypertension. Hence, careful examination of the optic nerve should be performed before any treatment is given.
In order to examine the optic nerve, a patient must be looking in a direction which allows the ophthalmologist to analyze the optic nerve head (which is located in the plane of the retina). Currently, a patient is asked to look at objects in the ophthalmologist's office or at a light positioned to one side of the patient's head. In this technique, the patient's free eye is used to fixate on the object and the optic nerve head in the patient's eye under examination becomes exposed because it follows the free eye. This is a time consuming process since it is difficult for the patient to fixate on a particular object when an examining lens is pressed against one of the patient's eyes. In addition, fixation by this technique in functionally monocular patients is not possible because they do not have a fellow eye with which they can look at the object. This situation is often aggravated in glaucoma patients by a constricted and fixed pupil.